Typical blood oxygenators may be used as artificial cardiorespiratory devices, for example, during cardiopulmonary bypass surgery. Such oxygenators serve as an artificial respiratory system for a patient at a time when the patient is unable to rely on his own respiratory system, e.g. during surgery. These devices act temporarily as a patient's heart and lungs, circulating, adding oxygen to and removing carbon dioxide from a patient's blood while the patient's own heart and lungs are inactive.
It follows that a desirable oxygenator approximates as closely as possible the conditions and components of a patient's respiratory system. Forces mechanically applied to the blood as it flows through the oxygenator, which most closely simulate those normally experienced within the body, are safest and best for the patient's welfare.
Thus, the ambient conditions of existing oxygenators are designed to facilitate careful monitoring during use. For example, the Affinity™ Oxygenation System from Medtronic is clear so that the fluid flowing through the system can be monitored. It is also advantageous that conditions within an oxygenator can be adjusted so that they better resemble those normally experienced in the patient's body. To this end, typical oxygenators may be attached to other components of an oxygenation system, such as adjustable pumps to regulate the flow of blood through the oxygenator or an integrated heater, or cooling device to keep the blood at a desired temperature. Generally, during bypass surgery, the principal blood handling components of an artificial respiratory system would include an oxygenator, an arterial filter and a venous reservoir. These components are generally single-use disposable products.
One condition present in a typical oxygenator that deviates from the normal conditions of the patient's body is the presence of air bubbles in the fluid as it enters the oxygenator. Generally, air is present in an oxygenator before it is used for the first time. This air continues to be present when fluid is first put into the oxygenator and may appear as bubbles in the fluid. Under typical circumstances, the bubbles are removed during the priming of the device. Usually, removal of air bubbles occurs on the distal side of the fiber bundle. Then, any air bubbles on the proximal side must be forced through the fiber bundle to the distal side in order to be removed. Biocompatible coatings and the presence of blood in the device make removal of the air bubbles difficult, as they are unlikely to pass through the fiber wall or through the fiber bundle to the distal side.
These bubbles can cause a number of difficulties in that they may physically obstruct the actual flow of the fluid through the device. The bubbles could also potentially pass through the device and be sent back to the patient, which could cause injury to the patient.
Therefore a means of debubbling the fluid on the proximal side of the fiber bundle is desirable. Furthermore, a means that could be used to access the blood as it enters the oxygenator would be desirable.